T.R. Knight Says 'George O'Malley Will Always Claim My Heart' After Surprising Grey's Anatomy Episode

Grey's Anatomy: George O’Malley Returns in Meredith Grey's Dream as She Battles COVID-19

The surprises keep on coming for Grey's Anatomy fans!

T.R. Knight, who played George O'Malley on Grey's Anatomy from 2005 to 2009, is expressing his love for the fan-favorite character — and his costar, Ellen Pompeo.

"George O'Malley will always claim my heart," Knight, 47, wrote on Instagram Thursday. "Thank you to Ellen, Chandra, Jim, Krista, and all the familiar faces for once again sharing your beautiful light."

Later, he added a tribute to Pompeo and how much he enjoys the actress, 51, both as a scene partner and a friend.

"Ellen is the kind of actor I’m endlessly grateful to act with," he wrote. "She’s the embodiment of truth. George and Meredith love each other, for sure, but I don’t think he can hold a candle to love I have for Ellen."

"I’m so lucky to have a friend like you," Pompeo responded in the comments.

Knight starred alongside Ellen Pompeo (Meredith Grey), Chandra Wilson (Miranda Bailey), and James Pickens Jr. (Richard Webber) for the first five seasons of the long-running medical drama.

Vivian Zink/Walt Disney Television via Getty T.R. Knight as George O'Malley

The actor, who spent time on Broadway and currently appears opposite Kaley Cuoco in HBO Max's The Flight Attendant, shared a photo with his former costars on Instagram after Thursday night's episode of Grey's Anatomy — on which he makes a surprise appearance.

ABC Chandra Wilson, T.R. Knight, Ellen Pompeo, James Pickens Jr.

RELATED: Grey's Anatomy: George O’Malley Returns in Meredith Grey's Dream as She Battles COVID-19

In the episode, Meredith is battling the novel coronavirus (COVID-19), and George appears in one of her dreams on the beach. Earlier this season, Patrick Dempsey returned to the show as well to play Derek Shepherd — who died in an April 2015 episode — in one of Meredith's dreams.

“Wonderful and completely surprising things are absolutely possible,” executive producers Andy Reaser and Meg Marinis told PEOPLE last month of cast returns.

Although Knight has been off the show for a decade, he and Pompeo, 51, have remained close friends.

RELATED: Patrick Dempsey Says Fan Reaction to His Grey's Anatomy Return Has Been 'Overwhelming'

In March, the pals shared a selfie from a get-together.

"Old friends are the BEST friends @t.r.knight... but like we aren’t old... we’ve just known each other for a very long time yes yes that’s it...." Pompeo wrote in the caption for the snap.

Knight reposted Pompeo's post, adding, "I’m just happy we met when we were fetuses. ❤️"